1. Field of Invention
This invention relates generally to improved chemical processes for the synthesis of arylamine compounds, and to the use of such arylamine compounds in producing overcoating layers for electrophotographic imaging members. In particular, this invention provides a process for forming a 4-aminobiphenyl derivative arylamine compound, such as N,N-[3-carboxypropyl phenyl]-4-aminobiphenyl or its alkali metal salt, using a direct hydrogenation reaction on a carboxylate salt.
2. Description of Related Art
In electrophotography, an electrophotographic substrate containing a photoconductive insulating layer on a conductive layer is imaged by first uniformly electrostatically charging a surface of the substrate. The substrate is then exposed to a pattern of activating electromagnetic radiation, such as, for example, light. The light or other electromagnetic radiation selectively dissipates the charge in illuminated areas of the photoconductive insulating layer while leaving behind an electrostatic latent image in non-illuminated areas of the photoconductive insulating layer. This electrostatic latent image is then developed to form a visible image by depositing finely divided electroscopic marking particles on the surface of the photoconductive insulating layer. The resulting visible image is then transferred from the electrophotographic substrate to a necessary member, such as, for example, an intermediate transfer member or a print substrate, such as paper. This image developing process can be repeated as many times as necessary with reusable photoconductive insulating layers.
In image forming apparatus such as copiers, printers and facsimiles, electrophotographic systems in which charging, exposure, development, transfer, etc. are carried out using electrophotographic photoreceptors have been widely employed. In such image forming apparatus, demands for speeding up of image formation processes, improvement in image quality, miniaturization and prolonged life of the apparatus, reduction in production cost and running cost, etc. are increasingly growing. Further, with recent advances in computers and communication technology, digital systems and color image output systems have been applied also to the image forming apparatus.
Electrophotographic imaging members (i.e. photoreceptors) are well known. Electrophotographic imaging members are commonly used in electrophotographic processes having either a flexible belt or a rigid drum configuration. These electrophotographic imaging members sometimes comprise a photoconductive layer including a single layer or composite layers. These electrophotographic imaging members take many different forms. For example, layered photoresponsive imaging members are known in the art. U.S. Pat. No. 4,265,990 to Stolka et al., which is incorporated herein by reference in its entirety, describes a layered photoreceptor having separate photogenerating and charge transport layers. The photogenerating layer disclosed in the 990 patent is capable of photogenerating holes and injecting the photogenerated holes into the charge transport layer. Thus, in the photoreceptors of the 990 patent, the photogenerating material generates electrons and holes when subjected to light.
More advanced photoconductive photoreceptors containing highly specialized component layers are also known. For example, a multilayered photoreceptor employed in electrophotographic imaging systems sometimes includes one or more of a substrate, and undercoating layer, an intermediate layer, an optional hole or charge blocking layer, a charge generating layer (including a photogenerating material in a binder) over an undercoating layer and/or a blocking layer, and a charge transport layer (including a charge transport material in a binder). Additional layers such as one or more overcoat layer or layers are also sometimes included.
In view of such a background, improvement in electrophotographic properties and durability, miniaturization, reduction in cost, etc., in electrophotographic photoreceptors have been studied, and electrophotographic photoreceptors using various materials have been proposed.
For example, JP-A-63-65449 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”), which is incorporated herein by reference in its entirety, discloses an electrophotographic photoreceptor in which fine silicone particles are added to a photosensitive layer, and also discloses that such addition of the fine silicone particles imparts lubricity to a surface of the photoreceptor.
Further, in forming a photosensitive layer, a method has been proposed in which a charge transfer substance is dispersed in a binder polymer or a polymer precursor thereof, and then the binder polymer or the polymer precursor thereof is cured. JP-B-5-47104 (the term “JP-B” as used herein means an “examined Japanese patent publication”) and JP-B-60-22347, which are incorporated herein by reference in their entirety, disclose electrophotographic photoreceptors using silicone materials as the binder polymers or the polymer precursors thereof.
Furthermore, in order to improve mechanical strength of the electrophotographic photoreceptor, a protective layer is formed on the surface of the photosensitive layer in some cases. A crosslinkable resin is used as a material for the protective layer in many cases. However, the protective layer formed by the crosslinkable resin acts as an insulating layer, which impairs the photoelectric characteristics of the photoreceptor. For this reason, a method of dispersing a fine conductive metal oxide powder (JP-A-57-128344) or a charge transfer substance (JP-A-4-15659) in the protective layer and a method of reacting a charge transfer substance having a reactive functional group with a thermoplastic resin to form the protective layer have been proposed. JP-A-57-128344 and JP-A-4-15659 are incorporated herein by reference in their entirety.
However, even the above-mentioned conventional electrophotographic photoreceptors are not necessarily sufficient in electrophotographic characteristics and durability, particularly when they are used in combination with a charger of the contact charging system (contact charger) or a cleaning apparatus such as a cleaning blade.
Further, when the photoreceptor is used in combination with the contact charger and a toner obtained by chemical polymerization (polymerization toner), a surface of the photoreceptor is stained with a discharge product produced in contact charging or the polymerization toner remaining after a transfer step to deteriorate image quality in some cases. Still further, the use of the cleaning blade in order to remove the discharge product adhered to the surface of the photoreceptor or the remaining toner increases friction and abrasion between the surface of the photoreceptor and the cleaning blade, resulting in a tendency to cause damage of the surface of the photoreceptor, breakage of the blade or turning up of the blade.
Furthermore, in producing the electrophotographic photoreceptor, in addition to improvement in electrophotographic characteristics and durability, it becomes an important problem to reduce production cost. However, in the case of the conventional electrophotographic photoreceptor, the problem is encountered that coating defects such as orange peel appearances and hard spots are liable to occur.
The use of silicon-containing compounds in photoreceptor layers, including in photosensitive and protective layers, has been shown to increase the mechanical lifetime of electrophotographic photoreceptors, under charging conditions and scorotron charging conditions. For example, U.S. Patent Application Publication US 2004/0086794 to Yamada et al., which is incorporated herein by reference in its entirety, discloses a photoreceptor having improved mechanical strength and stain resistance.
However, the above-mentioned conventional electrophotographic photoreceptor is not necessarily sufficient in electrophotographic characteristics and durability, particularly when it is used in an environment of high heat and humidity.
Photoreceptors having low wear rates, such as those described in US 2004/0086794, also have low refresh rates. The low wear and refresh rates are a primary cause of image deletion errors, particularly under conditions of high humidity and high temperature. U.S. Pat. No. 6,730,448 B2 to Yoshino et al., which is incorporated herein by reference in its entirety, addresses this issue in its disclosure of photoreceptors having some improvement in image quality, fixing ability, even in an environment of high heat and humidity. However, there still remains a need for electrophotographic photoreceptors having high mechanical strength and improved electrophotographic characteristics and improved image deletion characteristics even under conditions of high temperature and high humidity.